


Non Compos Mentis

by WickedFollower



Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell (Undertale), Character Death, Other, Violence
Language: English
Status: Completed
Published: 2019-07-23
Updated: 2019-07-23
Packaged: 2020-07-11 18:00:26
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,440
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/19932181
Author URL: https://archiveofourown.org/users/WickedFollower/pseuds/WickedFollower
Summary: Sometimes the best of intentions lead us to our own early graves.





	Non Compos Mentis

**Author's Note:**

> Had this idea at work one morning, and it took a very dark end as i wrote it. 
> 
> But please, enjoy!!

“ASTER! ASTER GET DOWN HERE!” Sans was furious! He had just spent thirteen hours working only to come home to this? Sans placed the fidgeting babybones down in a small playpen by the corner. The babybones watched as Sans began to pick up plates left on the coffee table, “ASTER, I KNOW YOU FUCKIN HEAR ME! DON’T MAKE ME COME UP THERE!” A loud groan could be heard from the second floor, then a door slamming open and closed. “My name has a g in it by the way, you can do the least by pronouncing it right. What is it?” A young teenager stood by the top of the stairs, Sans looked at the boy. He was exhausted, and didn’t want to dive right into a fight over the pronunciation of words. He frowned, “I thought I told you, that if you were going to be homeschool you’d do basic chores while I’m at work?” Sans levitated the trash bin to the living room to finish picking up the trash left.    
  
The teen sighed, “I did do something! I did the laundry!” He huffed as he walked down the stairs, Sans sighed seeing the teen pout. As he put the trash bin back he peeked into the laundry room, it did in fact have a pile of clean clothes on the small counter Sans put in there to help hold clothing and extra supplies. “Aster, part of doing the laundry is folding it as well. Not just washing and drying it.” He heard a distinct mocking voice from the living room, Sans did not sign up for this part. 

After he’d moved out he’d found this house, it was abandoned so he bought it from the town. It was cheap and needed some repairs but the area he’d moved to was the cheapest area in the underground. But after about a year, he’d gotten a visit from the royal guard. And with them were his two younger brothers, one still a babybones. His parents had been killed in a religious persecution in New Home. Most monsters blamed skeletons for their banishment for some reason, some saying they invited death and destruction to those around them. After talking to the guard and going to their old house to get their things Sans took over as parent. He made it a point to fix up the two other rooms for them, as well as baby proofing the house. And it took time, hell, it took everything Sans had not to backtrack and send them off to someone else. But in reality, where would he send them? There was no where.    
  
Sans came back to the living room, Aster was sitting on the couch watching the baby. Sans sat next to the boy, “He bit someone today.” A laugh let the teen, the baby was teething. Sharp fangs peeking from the bone. “I had to talk with the parents and the daycare guy. They were pissed!” The baby looked up at them, a teething toy in there mouth. “Paps is a ferocious monster! Not be messed with, i bet that other kid was doing something!” Sans shook his head, these two were going to be the death of him one day. “I’m sure he will be, but that doesn’t change the fact he got kicked out. There's only one more day care this side of the underground left. It’s in waterfall, it doesn’t open till after I’m working. So I’d need you to drop him off before starting on your school work.” Aster looked to his older brother, large black bags stained under his eye sockets.   
  
Aster nodded, he knew his brother was tired. He knew that the outside world was slowing going to shit. He’d caught some new snippets when Sans watched it in the morning. The king, after the death of his children and the abandonment of his wife, had issued the new law to make the underground stronger. Kill or be killed. He’d seen Sans come home with cuts or bruises, sometimes worse wounds. But Sans never spoke about it. “Yeah, I can do that.” Sans nodded and got up, most likely to begin dinner. Aster watched the baby babble, he needed to make sure he was careful when dropping Papyrus off tomorrow. His brother trusted him, both of them.    
  
~~ 

  
  


Sans was late, it was well past his time to be home and Gaster was worried. He’d already gone to retrieve Papyrus as well, seeing as the daycare was about to close for the day. The baby was fast asleep in his playpen while Gaster paced the living rooms length. Gaster knew Sans could protect himself, he was strong. But that didn’t mean he didn’t worry, Sans was a handyman of sorts. At least that's what he told him, so he traveled for work. He went almost everywhere in the underground. But he was always home by dusk, or at least what the underground called dusk.    
  
Suddenly there was yelling outside, it sounded like a fight. Gaster rushed to the door, quickly looking outside. He couldn’t see very well, but the fight sounded close to the house. He opened the door as Sans was flung backwards. Gaster gasped, Sans fell into the snow. An Icecap came into his line of sight, it looked crazed. Eyes glazed over and mouth wide open fog coming out in a steady stream of breath. Sans was covered in scuff marks, cracks could be seen on his arms and skull.   
  
“Sans!” Gaster made to run over to him, but Sans eye lights stopped him. Sans got up, body weak from having to fight for so long. “Aster, get back inside and lock the door!” Gaster didn’t move, to scared after the Ice Cap looked at the younger skeleton. The icecap moved towards Gaster, SAns threw a bone at it. Gaster looking at the monster, fear striking him deep. The Icecap wasn’t deterred from his new target. Gaster didn’t know what to do! He’s never been in a situation like this! The Icecap formed some ice bullets, and launched them at the teen. Sans teleported over the crazed monster, throwing his body into it. The bullets barely missed Gasters body. “ASTER I SAID TO GET BACK INSIDE! NOW!” Gaster bolted for the door, quickly shutting it and locking the lock. He then picked up Papyrus and run deeper into the house, going to hide in a cabinet in the laundry room. Soft purple tears rolled down his face, what was this? Why was Sans being attacked? Was this the effect of the new law by the king?   
  
Gaster stayed in the cabinet for what felt like hours, papyrus had woken up some time ago and was getting bored. Gaster tried to keep the baby entertained but it was hard when there was barely room to breath with them both in there. “Shhhh paps, we have to be quiet!” The baby whined a bit louder, Gaster tried to softly bounce the baby a bit. He’d Sans do it when the baby was fussy. Gods, was Sans dead? Does that mean Gaster had to raise Papyrus by himself? Where would they live? How would Gaster support them both? He wasn’t old enough to get a job! He was barely out of his stripes!   
  
There was a loud noise from the living room, Gaster stopped breathing. This was it, it was over. More tears spilled from his eyes. Sans was dead, nothing but dust in the cold wind outside the house. And now both him and papyrus would be a pile of it in this cabinet. He pressed a shaky kiss to Papyrus’s forehead, “I’m so sorry paps, I love you.” They both wait, the silence seeming to suffocate Faster. Finally footfalls could be heard in the laundry room. The cabinet was yanked open, Gaster let out a loud growl. He doesn’t know why, his fate was already sealed. “Ay, don’t fuckin growl at me. Get out of the damn cabinet.” Gaster looked at the monster, it was Sans! Gaster felt relief flood his body, “Oh thank the stars! Sans, I thought you were dead!” Gaster launched himself at Sans. The tears pouring down his face as he sobbed into his older brother, Sans wrapped his arms around both skeletons. Gaster was so relieved, Sans had not only lived but had come for them. 

Gaster looked at his brother and froze, blood red marrow was pouring from Sans face. He was missing a tooth. He had small cracks all over his skull, and his eyes still burned in his eye sockets. “s-Sans?” Sans shook his head, “I’m fine, but we have some new house rules. Let go to the living room.” Gaster just nodded as they stood up, Gaster still holding Players to his chest. This was going to be a long night, and Gaster didn’t know what the future held for them any longer.   
  
~~   
  
It’d been some years since Sans was first attacked. Sans had made new rules, Gaster was not to leave the house without Sans. There was a new curfew of dusk. If Gaster was outside he was to not to speak or stop for anyone but family. Sans was going to change his work schedule to keep everyone safe. In all this time Gaster had graduated school, and was applying to jobs. Papyrus was a whirlwind of energy, having learned how to run before walking. Gaster was stuck teaching him during the day, most of the schools in the area had been attacked for what Sans had called ‘free exp’. It’d take a few days for Gaster to understand what he’d meant. And it made him sick. This world had gone to shit right before his eyes and Gaster was sick.    
  
He wanted to change this sick world. He wanted to bring that light of hope back from the cold empty hands of death that had rested over this world. So he set out to find solutions, and he thought he did. He went to the king one day, not telling Sans or Papyrus of his plans. He would show the man his plans to help the underground, and fix this world of death.    
  
Gaster laid on the ground of the throne room, his body shivering. Marrow filled his vision, his skull ached. The king was just sitting in his throne. “You are a brave fool W. D. Gaster.” The kings voice made Gaster feel empty. “But I am no fool.I see some use of your ideas.” The king stood, slowly stalking his form on the ground, “You will be my new royal scientist, you will make these machines and “ _ help the underground _ ”. Now get up and leave. Your work beings tomorrow.” The King walked past him, and he felt his body sag. He hadn’t expected the King to be so cruel, nor for his form of punishment for suggesting the underground was broken. He slowly stood, two guards stood silent in the room having seen it all. But even with his wounds Gaster felt he had accomplished something today, something that would benefit the underground far more than the King's laws. He made his way home, too tired to worry about Sans or Papyrus reactions to his actions. He did this for them, for all the monsters of this world.

  
  


~~

More years have passed. Sans was older, more beat up than he’d say. Papyrus was well into his recruitment training for the guard. And Gaster, well Gaster was well into losing his mind to his latest experiment. Under the King's firm orders, he was to look into the magic of the barrier. And what Gaster found made his cracked skull pulse in unfathomable pain. He tried telling the King that the barrier was unbreakable by mere monster hands. Than had earned him a month's worth of torture. The King was on his last shred of sanity, the whole underground knew. But Gaster would not let his madness take his mind. But anyone who knew the skeleton closely knew he was losing it.   
  
Sans often found him in the homes basement giggling to himself over the info he was looking at from the barrier. “Oh, oh no. Not possible. Hehehehehe, yes, I know. How could I not?” Gaster came running to the King one day, “Your majesty! I have something to show you!” The King merely looked on, his cold dead eyes not seeing anything before him. Many speculated he had gone blind, but none would dare check. “Hehehehehe, I found it! The answer to your questions!”   
  
Gaster didn’t wait, he told the King. How he could make a machine to power the underground indefinitely while also weakening the barrier! He hadn’t needed to convince the King, he had approved it immediately. And so, the CORE was built. But it didn’t stop there, With the creation of the CORE Gaster’s mind seemed to run away from him faster. And Sans finally had enough of it. “Aster, what the ever loving fuck are ytou doing!?” Sans had found the skeleton just staring into the lava surrounding the CORE. Sans walked closer to the man, his body was hunched over the walkways railing. “Aster, hello? Answer me goddamnit!” Sans was closer now and could see Gaster was mouthing something.    
  
Sans jumped as Gaster stood up straight, he looked to the smaller skeleton, “I spoke to God and he could only scream in pain.” Sans was stunned for a second, “I spoke to God and he could only scream in pain.” Gaster just repeated himself, did it over and over and over again. Sans spoke, his voice soft, “Gaster?” Gaster gave him a soft smile, but he didn’t say anything. He then quickly pulled himself over the railing. Sans raced forward, trying to reach for his brother. But Gaster had flung himself over the edge.   
  
Sans screamed for his brother, tears falling from his face. What had he brother done? What had the King done to his brother? Sans looked to the CORE, this is what did this to his Brother. This damn machine had drove his brother to death. In his anger he teleported to the machine, using his claws he carved something into the metal. “The CORE killed W. D. Gaster.” Sans would make sure no one forgot what had happened, that a great monster had given his life to the pursuit to make this world better. But little did he know that the world had already forgotten him, even his youngest brother. Sans kept Gasters last word in his mind for years, “ _ I SPOKE TO GOD AND HE COULD ONLY SCREAM IN PAIN.”  _

**Author's Note:**

> Comment and kudos if you liked it and would like to see more of this kind of stuff!!


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